Species Transport: Boundary Conditions at Geometry Interface
 

Dear Members,

I am simulating the diffusion (no convection) of a gas first across a volume of air, and then into and across a volume of water as shown below. This is how I have modeled the media:
a. I enabled species transport and defined a mixture with the components of gas, liquid-h2o and air.
b. Then, I set pre-fixed values of the mass fraction of liq-h2o in the AirMedium to zero, and the mass fraction of air in the WaterMedium to zero in the "Cell Zone Conditions" tab.

1) Air medium. The top surface of the cube (not visible) is defined as an inlet-vent with specified gas mass fraction. The hemisphere at the bottom is the boundary of the AirMedium and the WaterMedium

http://i.imgur.com/ZxmRagO.jpg


2) Water Medium. The Hemispherical cavity is the boundary of the WaterMedium and the AirMedium.

http://i.imgur.com/mXsI4RB.jpg

Another thing to be noted is, that I had specified connection at the boundary during meshing.


My problem is, how do I define these boundaries between the AirMedium and WaterMedium in the "Boundary Conditions" tab? Outflow, Outlet-vent, or Wall? I do not know the mass fraction of the gas at this boundary.

Thanks in advance for the help. Any help will be very useful.